Network Working Group M. Smith, Editor
Request for Comments: DRAFT Netscape Communications Corp.
Obsoletes: RFC 2254 T. Howes
Expires: 7 November 2001 Loudcloud, Inc.
7 May 2001
The String Representation of LDAP Search Filters<draft-ietf-ldapbis-filter-01.txt>1. Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Discussion of this document should take place on the LDAP (v3)
Revison (ldapbis) Working Group mailing list <ietf-
ldapbis@openldap.org>. After appropriate review and discussion, this
document will be submitted as a Standards Track replacement for RFC2254.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
2. Abstract
The Lightweight Directory Access Protocol (LDAP) [RFC2251bis] defines
a network representation of a search filter transmitted to an LDAP
server. Some applications may find it useful to have a common way of
representing these search filters in a human-readable form. This
document defines a human-readable string format for representing the
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INTERNET-DRAFT String Representation of LDAP Filters 7 May 2001
The valueencoding rule provides that the characters "*" (ASCII 0x2a),
"(" (ASCII 0x28), ")" (ASCII 0x29), "\" (ASCII 0x5c), and NUL (ASCII
0x00) are represented as the backslash "\" character (ASCII 0x5c)
followed by the two hexadecimal digits representing the ASCII value
of the encoded character.
This simple escaping mechanism eliminates filter-parsing ambiguities
and allows any filter that can be represented in LDAP to be
represented as a NUL-terminated string. Other characters besides the
ones listed above may be escaped using this mechanism, for example,
non-printing characters. Each octet of the character to be escaped
is replaced by a backslash and two hex digits, which form a single
octet in the code of the character.
For example, the filter checking whether the "cn" attribute contained
a value with the character "*" anywhere in it would be represented as
"(cn=*\2a*)".
Note that although both the substring and present productions in the
grammar above can produce the "attr=*" construct, this construct is
used only to denote a presence filter.
5. Examples
This section gives a few examples of search filters written using
this notation.
(cn=Babs Jensen)
(!(cn=Tim Howes))
(&(objectClass=Person)(|(sn=Jensen)(cn=Babs J*)))
(o=univ*of*mich*)
(seeAlso=)
The following examples illustrate the use of extensible matching.
(cn:1.2.3.4.5:=Fred Flintstone)
(cn:=Betty Rubble)
(sn:dn:2.4.6.8.10:=Barney Rubble)
(o:dn:=Ace Industry)
(:1.2.3:=Wilma Flintstone)
(:dn:2.4.6.8.10:=Dino)
The first example shows use of the matching rule "1.2.3.4.5".
The second example demonstrates use of a MatchingRuleAssertion form
without a matchingRule.
The third example illustrates the use of the ":dn" notation to
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INTERNET-DRAFT String Representation of LDAP Filters 7 May 2001
indicate that matching rule "2.4.6.8.10" should be used when making
comparisons, and that the attributes of an entry's distinguished name
should be considered part of the entry when evaluating the match.
The fourth example denotes an equality match, except that DN
components should be considered part of the entry when doing the
match.
The fifth example is a filter that should be applied to any attribute
supporting the matching rule given (since the attr has been omitted).
The sixth and final example is also a filter that should be applied
to any attribute supporting the matching rule given. Attributes
supporting the matching rule contained in the DN should also be
considered.
The following examples illustrate the use of the escaping mechanism.
(o=Parens R Us \28for all your parenthetical needs\29)
(cn=*\2A*)
(filename=C:\5cMyFile)
(bin=\00\00\00\04)
(sn=Lu\c4\8di\c4\87)
(1.3.6.1.4.1.1466.0;binary=\04\02\48\69)
The first example shows the use of the escaping mechanism to
represent parenthesis characters. The second shows how to represent a
"*" in an assertion value, preventing it from being interpreted as a
substring indicator. The third illustrates the escaping of the
backslash character.
The fourth example shows a filter searching for the four-byte value
0x00000004, illustrating the use of the escaping mechanism to
represent arbitrary data, including NUL characters.
The fifth example illustrates the use of the escaping mechanism to
represent various non-ASCII UTF-8 characters.
The sixth and final example demonstrates assertion of a BER encoded
value.
6. Security Considerations
This memo describes a string representation of LDAP search filters.
While the representation itself has no known security implications,
LDAP search filters do. They are interpreted by LDAP servers to
select entries from which data is retrieved. LDAP servers should
take care to protect the data they maintain from unauthorized access.
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INTERNET-DRAFT String Representation of LDAP Filters 7 May 2001
Tim Howes
Loudcloud, Inc.
599 N. Mathilda Ave.
Sunnyvale, CA 94086
USA
+1 408 744-7509
howes@loudcloud.com
10. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
11. Appendix A: Changes Since RFC 225411.1. Technical Changes
"String Search Filter Definition" section: replaced the "value" rule
with a new "assertionvalue" rule within the "simple", "extensible",
and "substring" ("initial", "any", and "final") rules. This matches
a change made in [RFC22521bis]. Added angle brackets around free-
form prose in the "attr", "matchingrule", and "value" rules.
Introduced the "valueencoding" and associated "normal" and "escaped"
rules to reduce the dependence on descriptive text.
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INTERNET-DRAFT String Representation of LDAP Filters 7 May 200111.2. Editorial Changes
IESG Note: removed note about lack of satisfactory mandatory
authentication mechanisms.
Header and "Authors' Addresses" sections: added Mark Smith as the
document editor and updated Tim's affiliation and contact
information.
Copyright: changed the year to 2001.
"Abstract" section: updated second paragraph to indicate that RFC2254 is replaced by this document (instead of RFC 1960).
"LDAP Search Filter Definition" section: made corrections to the
LDAPv3 search filter ABNF so it matches that used in [RFC2251bis].
In particular, the "at least one must be present" comment and the
"substrings" label were added to the SubstringFilter
initial/any/final sequence, the second element of the
AttributeValueAssertion was changed from "attributeValue
AttributeValue" to "assertionValue AssertionValue", and the
occurrences of "LDAPString" were replaced with "AssertionValue"
within the initial, any, and final elements of the substrings choice.
"String Search Filter Definition" section: clarified the definition
of 'value' (now 'assertionvalue') to take into account the fact that
it is not precisely an AttributeAssertion from [RFC2251bis] section4.1.6 (special handling is required for some characters). Added a
note that each octet of a character to be escaped is replaced by a
backslash and two hex digits, which form a single octet in the code
of the character (text taken from the [RFC2253bis] document).
"Examples" section: added four additional examples: (seeAlso=),
(cn:=Betty Rubble), (:1.2.3:=Wilma Flintstone), and
(1.3.6.1.4.1.1466.0;binary=\04\02\48\69). Replaced one occurrence of
"a value" with "an assertion value".
"Security Considerations" section: added references to [RFC2251bis],
[RFC2829bis], and [RFC2830bis].
"References" section: changed from [1] style to [RFC2251bis] style
throughout the document. Added entries for [RFC2829bis] and
[RFC2830bis] and updated UTF-8 reference to RFC 2279. Replaced RFC822 reference with a reference to RFC 2234.
"Acknowledgments" section: added.
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INTERNET-DRAFT String Representation of LDAP Filters 7 May 2001
"Appendix A: Changes Since RFC 2254" section: added.
"Appendix B: Changes Since Previous Document Revision" section:
added.
"Table of Contents" section: added.
12. Appendix B: Changes Since Previous Document Revision
This appendix lists all changes relative to the last published
revision, draft-ietf-ldapbis-filter-00.txt. Note that these changes
are also included in Appendix A, but are included here for those who
have already reviewed draft-ietf-ldapbis-filter-00.txt. This section
will be removed before this document is published as an RFC.
12.1. Technical Changes
"String Search Filter Definition" section: replaced all occurrences
of the "value" rule with "assertionvalue" within the "initial",
"any", and "final" rules. This was done to reflect changes made to
the ASN.1 definition of the Filter in [RFC2251bis]. Also, the
"escaped" rule was revised and a "hex" rule was added to allow any
character to be escaped.
12.2. Editorial Changes
"LDAP Search Filter Definition" section: updated the ASN.1 definition
of the Filter to match that used in [RFC2251bis]. Specifically, the
occurrences of LDAPString within the initial, any, and final elements
of the substrings element were replaced with AssertionValue.
"String Search Filter Definition" section: corrected truncated text
that described the valueencoding rule (the text was truncated after
(ASCII 0x29)). Added a note that each octet of a character to be
escaped is replaced by a backslash and two hex digits, which form a
single octet in the code of the character (text taken from the
[RFC2253bis] document).
"Examples" section: replaced one occurrence of "a value" with "an
assertion value".
References: updated references to refer to LDAPBis WG documents.
"Appendix C: Loose Ends": removed this section entirely.
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